Equilibrium and kinetic studies on the removal of some metal ions using biogenic amorphous silica

In the present study agricultural waste (rice husks) was used for the production of biogenic silica. The resulting material was obtained by incineration of rice husks at a temperature of 800 degrees C and was characterized by means of XRD, FTIR, SEM-EDS, Hg-porosimetry and N-2-adsorption. The adsorption ability of the rice husks ash towards Fe(III), Pb(II), Cr(III) and Cu(II) ions in single- and multi-component aqueous solutions was studied in a batch system. The effects of contact time, acidity of initial solutions and metal ion concentrations were followed. Different models were used to determine the adsorption mechanism. Equilibrium experimental data were fitted to linear Langmuir and Freundlich models. The maximum adsorption capacities for single- and multi-component adsorption were calculated.